The present invention is related to shaft lining forming methods and apparatus and particularly to such methods and apparatus for forming vertical or upright monolithic concrete lining in situ within mine shafts or similar excavations.
In mining operations, central mine shafts, winding shafts, blind shafts, and ventilation shafts are vertical and lead downwardly and beyond horizontal tunnels. Such shafts may extend from the earth surface vertically downward to adjoining tunnels, or they may extend from one tunnel vertically to another tunnel at a different elevation. Futher, vertical shafts, termed "blind shafts," extend downwardly from one tunnel to a closed bottom end. For mining purposes, nearly all vertical shafts must be lined with concrete or masonry to prevent the shaft walls from collapsing or "sloughing" and isolating the adjoining tunnels. During the drilling operation of such upright shafts, a liquid "drilling mud" is utilized to assist the drilling operation and to prevent the shaft walls from sloughing onto the boring head. Ordinarily, the shaft is nearly completely filled with such drilling mud and must be pumped dry before conventional lining operations can take place.
Various apparatus and methods have been produced for placing shaft linings in upright dry excavations. Most presently used apparatus and methods deal with the application of monolithic concrete lining rather than the application of masonry block or brickwork lining.
U.S. Pat. No. 411,981 granted to W. Davis discloses a method of cementing cisterns or wells. The disclosed process must be performed during the excavation process since the bottom of the shaft is utilized to support a retractable cylindrical form. The excavation is taken to a prescribed depth, then a form is laid in place at the bottom of the excavation. Concrete or cement is then poured about the form and allowed to harden between the form walls and shaft. Once the cement has hardened, the form is removed and the excavation is continued on downwardly past the ring of concrete previously formed. It is intended that this ring be utilized as both a portion of the shaft lining and as a "curbing" to hold the shaft walls intact during the remainder of the excavation operation. It is not disclosed how the shaft walls are lined between the cement rings or "curbing".
U.S. Pat. No. 233,826, granted to W. Wilson on Oct. 26, 1880, discloses an apparatus for lining wells. This device is comprised of two independent form members, one for defining an exterior lining surface, and the remaining form for producing the lining interior surface. In operation, after the shaft has been excavated to a required depth, a section of cement tube is placed within the shaft and pressed against the bottom shaft end. This tube must have inside and outside diameters equal to the corresponding dimensions of the lining. Once this tube has been placed within the bottom of the shaft, the inside or core cylinder is lowered into the tube with a portion of its length extending above the top tube end. The outer cylinder is also put in place about the outside of the tube and also extends upwardly above the upper tube edge. A tubular receptacle is thereby formed into which cement or concrete may be poured and allowed to harden. Once this cement or concrete has hardened, the two form members may be slipped upwardly over the newly formed lining section to form the next successive batch of concrete poured on top of the previously poured section. In this manner, the well lining is produced in a succession of independent pours from the shaft bottom to the top.
The "inchworm" movement of the form members is commonly known as "jump forming" and is especially used in current shaft lining operations. This process has been reasonably effective. However, this procedure necessitates that the shaft be dry and drilled oversize in order to accommodate the outside form member and further requires that workers be sent down the shaft in order to effectively operate the form members and spread the concrete evenly about the lining between the members. An additional problem with "jump forming", since it involves peak labor periods, is relatively low production rates.
U.S. Pat. No. 1,313,013 granted to C. Polysu on Aug. 12, 1919 discloses a method and apparatus for casing wells. This apparatus is similar to the Davis device in that the lining is formed in a downward direction from the top of the shaft and is formed while the shaft is being excavated. This particular device utilizes a boring head with a concrete slipform following behind. The lining may be poured after the boring instrument has excavated a shaft to a depth equal to the height of the form members. The slipform itself is simply an inner core member that forms the inside bore of the lining. Concrete is pumped downwardly to the slipform and outwardly into the area between the slipform and boring head.
As the shaft is excavated, the boring head moves downwardly and so does the slipform. Concrete is pumped into the area between the slipform and shaft as the slipform moves downwardly at a rate supposedly equal to the rate of excavation of the boring head. This rate is controlled to correspond to the setting time for the concrete so that the form lining supports itself within the shaft after disengagement from the inner core member.
At the end of the boring operation, the slipform must be left within the shaft, since the full weight of the shaft lining rests upon the lower portion thereof. The setting time of the concrete being delivered to the slipform must be timed precisely with the advancement of the boring tool. Therefore, the conditions of the soil surrounding the shaft area must be very carefully considered and extremely prompt action must be taken once soil conditions change. Otherwise, the lining is not formed at a correct rate. For example, if the lining were formed too quickly, the concrete could possibly not harden and could therefore fall apart once the slipform moved downwardly leaving the wet concrete to support itself. Should the boring head move to slowly, the concrete could harden within the delivery tube and halt progression of the lining at that point.
U.S. Pat. No. 3,827,244, granted to H. L. Walbro on Aug. 6, 1974, discloses a form for producing concrete linings in mine galleries, tunnels, shafts, or the like. A slipform is used by Walbro and is pulled directly behind a tunnelling cutter. It includes a relatively short forming member that receives and forms concrete about its periphery against the tunnel walls and a series of thrust members that are utilized to support the "green" concrete until it reaches a sufficiently stable form to support itself and withstand the pressure exerted by the earth around the tunnel. The thrust members are pulled along with the forming head at a rate such that the last thrust member leaves the concrete lining surface exposed as that surface reaches a hardened condition. It is the "shutters" or reinforcing rib members that are the central subject of this patent, not the specific details of a slipform. The slipform itself is pulled along as it receives concrete in a wet state by a boring mechanism.
Other patents of general interest are U.S. Pat. No. 3,270,511 granted on Sept. 6, 1966 to E. Colly and U.S. Pat. No. 3,768,267 Oct. 19, 1973 to N. Chlumecky. Also, further background material may be found by referring to my U.S. Pat. No. 3,877,855 granted Apr. 15, 1975.
The present invention relates to a method and apparatus whereby a freshly bored shaft having been previously filled with a liquid such as drilling mud may be lined in situ with concrete in a relatively continuous monolithic form by delivering wet concrete to two longitudinally spaced form members within the upright shaft and pumping the drilling mud from above the form members to the area below the form members to pressurize that area and thereby force the form members upwardly within the shaft as the concrete is received thereby. An outer form member of the two is sealed to the shaft wall through a movable hydraulic seal formed by the wet concrete. The inner core member is utilized simply to form the concrete about the shaft walls and define an inside bore of the finished lining. Wet concrete is delivered to the two form members through an elongated tube at a rate complementary to the rate of ascent for the two form members. This rate is timed in accordance to the setting time of the concrete such that the inside form member will leave the lining walls in a hardened, self-supporting state as it becomes disengaged therewith. No frictional engagement of any lining or shaft wall surfaces is required to perform the function of moving or lifting the slipform upwardly as concrete is simultaneously delivered to produce the formed monolithic lining.